The city is the poorest in "debt per capita" in Germany... And the fans could be willing but we need too much money. The "big deal" would be that anyone buys the stadium (50-60 Million Euro) but at this place it could hardly be used otherwisely than as for our football club. The investor won't make much money by this, except he takes some another lots of Millions to push FCK to Champions League.
Heartbleeding I think the only solution is to remove the stadium for building homes to sell or rent them or use the ground for some commercial issues. Then we need some Millions to buy ground around our center for Youth and training (called "Fröhnerhof"). There must be placed a new modern arena for around 35k visitors, a smaller one for youth and friendly matches and some buildings for administration. Then we could be able to survive in the second tier or even the third without having to sell all players who generate some money every year to nearly any price.
We have no chance with this stadium without being a good team in 1. Bundesliga. The stadium and its ground belong to the city (which is very poor) and we would always have to beg for lower annual rents.
It is a disaster which could be seen before since years by most of us. There where many chances to improve our situation. But looking back we (us fans and owners and the club's administration) always took the wrong way at almost every decision to choose.